This invention relates generally to stabilized temperature platform furnaces used to analyze organic liquids. More particularly it relates to the design of the L'vov platform used to retain an organic liquid sample in the furnace during direct analysis.
Graphite furnaces with an atmosphere of argon gas are employed with atomic absorption spectroscopy in the semiconductor industry to determine the purity of the chemicals that are used to diffuse onto the silicon oxide in semiconductors during manufacture. The purity of these chemicals is critical, since the presence of impurities will destroy the insulating property of silicon dioxide and cause the semiconductor device to fail.
Current analysis techniques employ the use of indirect chemical analysis or the use of pyrolitic graphite tube furnaces with a centrally located sample platform upon which is Placed the liquid to be analyzed. The indirect analysis technique requires the sample of organic liquid to be evaporated and the residue dissolved into an approximate 0.5 percent nitric acid aqueous solution. This slightly acidic solution is placed on the surface of the sample-holding L'vov platform and then evaporated.
Direct analysis of organic liquids requires multiple deposition and evaporation steps of the organic sample on the L'vov platform. This requires the deposit of relatively small volumetric quantities of the organic sample in droplet form because of the wetability of the L'vov platform used to hold the sample and the sample's tendency to flow off of the platform and reduce the quantity of liquid being analyzed. The organic liquids being analyzed have very low surface tension, compared to water, and the loss of some sample liquid from the platform is possible. To ensure sufficient accuracy of the parts per billion elemental analysis required, up to ten (10) samples of up to ten (10) microliters of the organic liquid have to be manually deposited in droplet form on and evaporated from the L'vov platform. The vapors are analyzed after each cycle. Reproducibility and consistency of the results is a major concern between each run of a multiple deposition-evaporation-analysis cycle. Each deposition in the cycle increases the risk of contamination. Accuracy and sensitivity of the analyses are hampered by the need to perform multiple depositions and evaporations of relatively small samples.
These problems are solved in the design of the present invention which employs an improved L'vov sample-holding platform in a graphite furnace to obtain direct elemental analyses of organic liquids by atomic absorption spectroscopy.